Revert "Occasionally the while loop can exit with no data (Probably recieving an EOF) before receiveing CMDline data from the certial port. Continue looping until cmdline is populated"

This reverts commit 83656a6ea81ce9b85c2f480e576fd02d8a58c357.

The systemvm/routers will reboot automatically if the systemvm.iso changes.
They will stuck during the startup due to this commit because the virtio-port are empty.